How to read the battery level of an iPhone or iPad

iOS lets you track the battery level and status of the device you’re running on, which is helpful if you’re overlaying some sort of battery indicator over your user interface. You could even write a trivial app to detect power outages just by plugging in a spare phone then waiting for the charge state to change.

To get started, first enable the isBatteryMonitoringEnabled property of the current device, like this:

UIDevice.current.isBatteryMonitoringEnabled = true

You can now read the current battery level as a value between 0.0 (flat) and 1.0 (fully charged) using this:

let level = UIDevice.current.batteryLevel

If you want to be notified every time the battery level changes you can register for the UIDeviceBatteryLevelDidChange notification (sent up to once a minute), and you can also register for UIDeviceBatteryStateDidChange notification to see when the charge state changes. Both of those require isBatteryMonitoringEnabled to be enabled.